The present disclosure relates to a light-emitting device and a method of manufacturing the same.
In laser light sources, power enhancement is a major task. Therefore, in addition to output enhancement in laser diode devices, semiconductor optical amplifiers (SOA) have been diligently studied as devices that amplify light from a laser light source. As used herein, optical amplifiers refer to amplifiers that directly amplify an optical signal in the form of light without converting the optical signal into an electrical signal, and the optical amplifiers have a laser structure without resonator, and amplify incident light with an optical gain thereof.
Since optical amplifiers have been developed mainly for optical communication, semiconductor optical amplifiers for a 405-nm band have rarely been put to practical use. A semiconductor optical amplifier for a 1.5-μm band that uses a GaInAsP-based compound semiconductor and has a tapered ridge stripe structure is known from, for example, Japanese Unexamined Patent Application Publication No. H5-067845. According to the technology disclosed in this patent publication, in the semiconductor optical amplifier, a mode field is expanded along an optical waveguide width by gradually widening the optical waveguide width in a tapered shape from a narrow optical waveguide satisfying single-mode conditions on an input side to an optical waveguide on an output side so as to enhance highest output in the semiconductor optical amplifier.
A typical laser diode device or a typical semiconductor optical amplifier has a laminate structure body formed on a base substrate. In this case, a typical laminate structure body is configured by laminating, in order from the base substrate, n-type compound semiconductor layers (specifically, an n-type cladding layer and an n-type light guide layer) doped with n-type impurities, an active layer, and p-type compound semiconductor layers (specifically, a p-type light guide layer and a p-type cladding layer) doped with p-type impurities.